gfauto: Add support for samplers (#1070)
gfauto: Add support for samplers (#1070)

This change adds support for samplers in shader jobs. The output AmberScript file contains commands to generate a default texture. 
google/graphicsfuzz,google/graphicsfuzz,google/graphicsfuzz,google/graphicsfuzz,google/graphicsfuzz,google/graphicsfuzz,google/graphicsfuzz